1. Field of the Invention
The present invention is related to a process for dealkylating alkyl phenols. More specifically, the present invention is directed to a thermal dealkylation process for alkylated phenols to yield phenol.
2. Description of the Prior Art
The market for phenol is much greater than that for alkylated phenols normally obtained from coal tar or from petroleum or coal hydrogenation. Thus, the production of phenol from alkylated phenols is an area which has received much attention from researchers.
Dealkylation of alkyl phenols by thermal cracking is known in the prior art. However, the prior art methods suffer from the disadvantage that not only does dealkylation occur, but there is also a substantial amount of dehydroxylation so that the less valuable benzene is formed instead of phenol.
It has been proposed to dealkylate an alkylated phenol by reacting hydrogen and the alkylated phenol over a solid catalyst, such as barium oxide, silica gel, nickel sulphide, aluminum oxide, and so forth, for a short period of time. However, in such a process, a large amount of the cresol present in the feed remains unchanged. Furthermore, there is conversion of part of the phenols present to benzene and other hydrocarbons.
Thus, there exists a need for a process whereby the alkyl substituent in an alkylated phenol may be removed without simultaneously removing the hydroxyl group.
It has been discovered by the present inventor that substituent alkyl groups may be removed from alkylated phenols by reacting a feed solution comprising a mixture of alkylphenols with hydrogen in the presence of water vapor, the reaction being conducted at elevated pressures and temperatures. It has been discovered that by hydrodealkylating alkyl phenols in the presence of water vapor, the conversion rate of the alkyl phenols as well as the selectivity for phenol, the desired product, are substantially improved.